Why the Same Diameter Wears Differently
A 40mm case from one manufacturer can wear like a 38mm from another, and like a 43mm from a third. The reasons are case construction, lug shape, and thickness — dimensions that are rarely foregrounded in marketing but matter enormously on the wrist.
This is why trying watches on before purchasing is always preferable to buying purely from specifications — but understanding the three key measurements at least allows you to make a more informed comparison.
The Three Measurements That Matter
Case diameter
The case diameter is measured across the widest point of the case, excluding the crown. It's the most commonly cited measurement and a useful starting point, but not the whole picture. Current mainstream sizing: 36–38mm is considered smaller/classic; 39–41mm is the most versatile range; 42–44mm reads as larger; 45mm+ is oversized and deliberately statement-making.
Lug-to-lug distance
The lug-to-lug distance (sometimes called the "vertical case size") is measured from the tip of the top lugs to the tip of the bottom lugs — the total height of the watch as it sits on the wrist. This is the measurement that most affects comfort. If the lug-to-lug is larger than your wrist width, the ends of the watch will overhang your wrist, creating a cantilevered effect that makes it wear uncomfortably and look disproportionate. A general rule: the lug-to-lug should be equal to or slightly less than your wrist width.
Case thickness
Case thickness determines whether the watch sits flat under a shirt cuff, whether it catches on things, and whether it has a dress-appropriate profile. Dress watches aim for under 8mm. Sports watches typically run 11–14mm. Automatic movements with a rotor require more space than manual or quartz movements, which is why slim automatics are technically challenging to produce.
Wrist Size Reference Table
| Wrist Circumference | Suggested Case Diameter | Max Lug-to-Lug |
|---|---|---|
| Under 160mm | 34–37mm | 44mm |
| 160–175mm | 37–40mm | 46mm |
| 175–190mm | 39–42mm | 48mm |
| 190–205mm | 41–44mm | 50mm |
| Over 205mm | 44mm+ | 52mm+ |
These are guidelines, not rules. Wrist shape (flat vs rounded), personal preference, and the specific case design all affect how a watch actually looks and feels. The table gives a starting point; wearing is the only reliable test.
Strap Width
The strap or bracelet width is measured at the point where it attaches to the lugs. It's listed as a "lug width" in specifications, typically between 18mm and 22mm for most watches. The lug width determines what replacement straps will fit — a watch with 20mm lugs takes 20mm straps, and nothing else will fit properly.
When buying a watch second-hand or vintage, check the lug width early: if it's an unusual size (17mm, 19mm, 21mm), aftermarket strap options may be very limited.
How to Check Specifications Before Buying
Most watch brands publish full specifications including lug-to-lug on their websites. If the spec sheet doesn't list lug-to-lug (which is unfortunately common), check user reviews and collector forums — enthusiasts typically photograph and measure their watches in detail. Sites like WatchUSeek and Reddit's r/Watches are reliable sources for real-world wearing reports on most popular models.
Unsure About Sizing? Try Before You Decide.
Visit our workshop in Durrës. We can show you reference pieces across sizes and help you find what actually works on your wrist — not just what looks good in a product photo. Family-owned and trusted since 2002.
Rruga Aleksander Goga · Durrës 2001 · Albania · +355 67 636 0510
Published by Iglisi Watch · Durrës, Albania · April 2026. This guide covers watch case sizing measurements as general purchasing guidance.